Single sideband and double sideband transmitters for data modems characteristically include a plurality of filters as well as other shaping and delay networks, for example, many conventional modems utilize a shaping filter, a vestigal sideband filter and a phase equalizer in the data transmitter. These circuits are expensive and relatively difficult to control insofar as producing a precise time response is concerned. Hence, given the increased emphasis on the reduction in the hardware required in data communication systems, any system which eliminates such circuits has obvious advantages as compared with the systems of the prior art.